Adjustable fail-safe rotary spring operator with a retaining band

ABSTRACT

A rotary spring-return actuator operator is provided with a multi-slot shaft and a clock type spring retained by a retaining band which encircles the spring in such a manner as to insure that the potential energy within the spring is safely contained during all operations requiring disassembly of the actuator assembly, and wherein the retaining band facilitates the in-field reversal of the spring direction or the adjustment of the spring preload by securing the spring to one or more of the slots on the multi-slot shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

BACKGROUND

The field of invention relates to rotary spring-return operators. Flator power springs have long been used as stand alone mechanical fail-safedevices. A spring return operator can also convert a double actingactuator to a fail safe single acting actuator when used in conjunctionwith, or coupled to, various types of power actuators, such as electric,pneumatic or hydraulic, to apply a torque to rotate a shaft that iscoupled with, or otherwise engaged to, the shaft of the said variouspower actuators when desirable. For instance, spring-return actuatorsare commonly used as a fail-safe assembly to rotate a device, such as avalve, to a predetermined “open” or “close” position, in the event ofthe interruption or failure of the air, water, or electrical supply tothe pneumatic, hydraulic, or electric actuators, respectively.

When used as a stand alone device a spring return operator typicallyreturns a device such as a manually operated valve to a pre-determinedsafe condition. The spring return operator can be directly mounted tothe device or can be adapted by means of linkage. To convert a doubleacting actuator to a single acting fail safe actuator take aspring-return operator coupled with a pneumatic actuator as an example,the air pressure applied to the pneumatic actuator will hold a device,typically a valve, in its normal operating position. Upon a loss of airpressure to the pneumatic actuator, the rotary spring return fail-safeoperator rotates the device to a safe condition, which depending on thespecific application, could be an open or a close position.

The use of a rotary spring-return operator requires a minimum amount ofenergy to be stored in the spring, also referred to as the springpreload, before the actuator can be operationally assembled to serve itsdesired purpose as an integral part of a larger assembly. Theinadvertent release of the stored energy stored in the spring, such as asudden spring pop-out during disassembly, has caused serious injuries topersonnel and equipment. Therefore, for reasons of safety, it isdesirable that appropriate provisions be made to prevent the inadvertentand potentially hazardous release of the stored energy within the springof a rotary spring actuator. The preferred embodiment described below isdesigned in such a manner to eliminate all inadvertent and potentiallyhazardous release of the spring's stored tension.

Moreover, it is desirable, and at times necessary, to make adjustmentsto the spring-return actuators in the field, such as adjusting thespring preload, or the direction of the spring-return actuator's outputrotation. In addition to the preferred embodiments' safety featuresdescribed herein, the preferred embodiment also enables a user toflexibly, yet safely, make in-field adjustments to the spring rotaryspring-return actuator assembly as desirable or necessary.

BRIEF SUMMARY OF THE INVENTION

When a wound rotary spring-return operator is engaged with a poweractuator in driving relation, the torque applied by the spring is ofsuch a magnitude as to effectively rotate a device, such as the shaft ofa valve, in the absence of a counter force applied to the shaft via thepneumatic, hydraulic or electric control actuator (coupled with thespring return operator). As such, the use of a rotary spring-returnoperator as explained requires a minimum amount of energy to be storedin the spring. Depending on the specific purpose served by thespring-return operator, or the specific device to which thespring-return operator is coupled to, it may be necessary to makeadjustments to the spring's tension prior to being functionallyinstalled, also referred to as the spring preload.

The subject spring-return operator has been designed in such a manner toeliminate all inadvertent and potentially hazardous release of thespring's stored tension during adjustment or disassembly byincorporating a retaining band that securely surrounds or encapsulatesthe spring. In addition to the enhanced safety features, the retainingband also facilitates a safe and feasible methodology to reverse therotational direction of the spring-return operator's output in thefield.

Moreover, the retaining band allows the user to safely and convenientlyremove the power spring assembly from the housing, allowing the user,for example, to adjust the spring preload in the field. Adjusting thespring preload is traditionally done by rotational clocking of theactuator, such as a pneumatic or hydraulic vane actuator, to the springhousing a multi-hole pattern in the spring cover plate. One problem withmethodology is that the spring shaft is timed to the actuator shaft,when the spring housing is clocked the mounting holes are no longertimed with the spring shaft. Typically the spring operator is mountedbetween the power actuator and the device being actuated, such as a flowcontrol valve, and a linkage has to be manufactured to allow for theexplained timing discrepancy. Consequently, if a preload change isrequired in the field, then the linkage will have to be remade. Onepreferred embodiment of the present invention avoids this timing problemby utilizing a multi-slot shaft in the spring-return operator to allowfor the spring preload to be incrementally adjusted while maintainingthe shaft to mounting bolt pattern orientation. This methodology is madefeasible by the retaining band used in the preferred embodiment, used tocontain the spring's stored energy, thus allowing for easy disassemblyof the spring-return operator so that the shaft can be clocked to thecorrect starting position in order to obtain the correct preload.

A preferred embodiment of the present invention is a rotaryspring-return operator comprising a housing having side walls, an endwall at one end thereof and open at its other end, a cover platedisposed in closing relationship with respect to the open end of thehousing, a rotatable shaft having one end journaled to said end wall, acoil spring interposed between and secured relative to said shaft andthe interior of said housing, and a retaining band securelyencapsulating the spring.

Another preferred embodiment of the present invention is rotaryspring-return operator comprising a housing having side walls, an endwall at one end thereof and open at its other end, a cover platedisposed in closing relationship with respect to the open end of thehousing, a rotatable multi-slot shaft having one end journaled to saidend wall; and a coil spring interposed between said shaft and theinterior of said housing. This preferred embodiment may further comprisea retaining band to contain the energy stored in the spring therebyfacilitating the removal of the spring from the housing when necessary.

Another preferred embodiment of the present invention is a rotaryspring-return operator which comprises a housing having side walls, anend wall at one end thereof and open at its other end, a cover platedisposed in closing relationship with respect to the open end of thehousing, a rotatable multi-slot shaft having one end journaled to saidend wall, coil spring means interposed between and secured relative tosaid shaft and the interior of said housing, and a retaining bandencapsulating the spring and secured to the side wall of the housing.

An embodiment of the present invention is also a retaining band for usein a rotary spring-return operator comprising a housing, a shaftrotatably journaled therein, and a spring interposed between and securedrelative to said shaft and the housing, wherein the retaining bandencapsulates the spring, and is used to secure the spring to thehousing.

Another embodiment of the present invention is a multi-slot shaftdesigned for use in a rotary spring-return operator which includes ahousing that rotatably receives the shaft and a spring interposedbetween and secured relative to said shaft and the housing, wherein themulti-slot shaft can be utilized to adjust the preload on thespring-return operator.

A further embodiment of the present invention is a method for safelyreversing the our direction of a spring-return operator including a coilspring retained in a retaining band housed in a spring housingcomprising the steps of releasing all the tension on the spring,disassembling the spring housing, removing the spring retained by theretaining band from the housing, flipping the spring 180 degrees; andreassembling the spring housing.

Another embodiment of the present invention is a method for safelyadjusting the spring preload of a spring retained in a retaining band,housed in a spring housing, and secured to a multi-slot shaft comprisingthe steps of releasing the tension on the spring, disassembling thespring housing, removing the spring retained by the retaining band,adjusting the multi-slot shaft according to a desirable spring preload,securing the spring to a vertical slot on the multi-slot shaftcorresponding to the desirable spring preload, and reassembling thespring housing.

The preferred embodiment of the present invention is also a method forsafely unwinding the spring of a spring-return operator and reversingthe direction of a spring retained by a retaining band used in a rotaryspring-return assembly coupled to a vane actuator, comprising the stepsof allowing the spring to rotate a vane of the vane actuator to movefully in a first direction, (1) using a retainer device to lock thespring-return operator, (2) disengaging the spring return operator fromthe vane actuator, (3) applying force to rotate the vane of the vaneactuator fully in a second direction, opposite to the first direction,(4) reengaging the spring return operator and the vane actuator, (5)applying force to the vane of the vane actuator in the second directionuntil the spring and the actuator torques are in balance, (6) removingthe retainer device, (7) removing the force applied to the vane to allowthe spring to rotate the vane actuator fully in the first direction,repeating steps (1) through (7) until all spring tension is released,disassembling the rotary spring-return assembly; inverting the retainedspring 180 degrees; and reassembling the rotary spring-return operator.

Finally, the preferred embodiment includes a method for safely windingthe spring after the spring reversal or any desired preload adjustmentscomprising the steps of allowing the vane of the vane actuator to movefully in the second direction, (1) reengaging the spring return operatorand the vane actuator, (2) applying force to rotate the vane fully inthe first direction, (3) using the retainer device to lock thespring-return operator, (4) disengaging the spring return operator fromthe vane actuator, (5) applying force to rotate the vane fully in thesecond direction, opposite to the first direction, (6) reengaging thespring return operator and the vane actuator, (7) applying force to thevane of the vane actuator in the first direction until the spring andthe actuator torques are in balance, (8) removing the retainer device,(9) applying force to the vane to rotate the vane fully in the seconddirection; and Repeating steps (1)-(9) until the spring is wound asdesired. In a preferred embodiment, steps (1)-(9) may be repeated untilthe force to balance the spring and the actuator is half the suppliedair pressure (80 psi upper supply pressure limit).

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1A is a perspective view illustrating a power actuated mechanism,in this instance a pneumatic vane actuator, operatively associated witha rotary spring-return operator, which is in turn operatively coupledwith a conventional valving member. FIG. 1B is an exploded view of thesame.

FIG. 2A is a perspective angled exploded view of the rotary springreturn operator.

FIG. 2B is a perspective side exploded view of the rotary spring returnactuator.

FIG. 3 is a top view of the spring assembly illustrating a coil springcontained in a retaining band secured around the spring using an anchornut.

FIG. 4A is a angled-side view of the spring housing assembly comprisingof the spring housing, which houses the spring assembly secured to it bya bolt 62 received by the anchor nut 36, and which through a centralopening in the housing receives the shaft 40, which is also secured tothe spring assembly. FIG. 4B is the side view of the same.

FIG. 5A is an angled-top view of the rotary spring-return operator, onthe side of the spring housing. FIG. 5B is an angled-top view of thesame, except that a spring retaining device 80 is inserted through thecentral opening of the housing to lock the shaft 40 and thus the springin place.

FIGS. 6A to 6E are the top view of the spring housing assembly of FIG.3, showing five different spring preload setting configurations usingthe five slots of a multi-slot shaft 40.

FIG. 7 is the side view of an device that may be used to wind or unwindthe spring of the spring return operator.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed embodiments of the present apparatus and method are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the apparatus and method that may be embodiedin various forms. As such, the specific structural and functionaldetails disclosed herein are not to be interpreted as restrictive orlimiting, but merely as a representative basis for teaching one skilledin the art to variously employ the present invention.

As illustrated in FIG. 1A and FIG. 1B, the rotary spring-return operator10 may be securely, though releasably, fastened or coupled to thehousing of a power actuator 12, which in this example, is a pneumaticvane actuator. The present invention is directed to a rotaryspring-return operator 10 a preferred embodiment of which is illustratedherein, and is neither limited to, concerned with, nor directed to, thespecific structural details of the power actuator 12 or the valvingmember 14. However, the structural details of the pneumatic vaneactuator 12, are illustrated in the U.S. Pat. No. 6,289,787 to Underwoodet al., and assigned to K-Tork International, Inc., which isincorporated herein by reference.

In the preferred embodiment, the rotary spring-return operator 10 may besecurely, though releasably, fastened or coupled to the plug shaft 17 ofa conventional valving member 14 using a coupling adapter 16 and abracket 15 as necessary. If the plug shaft 17 may be directly andcompatibly mated or fitted with the shaft 40 of the spring-returnoperator 10, the rotary spring-return operator 10 may be securely,though releasably, fastened or coupled to the plug shaft 17 and thus thevalving member 14 without using the coupling adapter 16 and bracket 15.The rotary spring-return operator 10 and the power actuator 12 may bedisposed in driving relation each other, and with plug shaft 17 ofconventional valving member 14. For example, the pneumatic vane actuator12 may maintain the valving member 14 in a normal operating conditionusing air pressure received through the vane actuator's opening 19 andexerting a force equal or greater than, and in the opposite directionto, the output force of spring return operator. In case of a loss ofpower to the power actuator, which in this case would be a loss of airpressure to the vane actuator, the rotary spring-return operator 10rotates the valving member 90 degrees or less depending on the positionof the stop bolt of the vane actuator 18, to a safe condition, whichdepending on the specific application, could be an open or a closeposition.

As illustrated by FIG. 2, the rotary spring-return operator 10 may bemainly comprised of a spring housing 20, a power spring assembly 30, ashaft 40, and a spring cover-plate 50. FIG. 3 further illustrates thepower spring assembly 30, wherein a retaining band 32, made out ofmaterial capable of withstanding and thus retaining the maximum possibleforce which may be stored in the spring 34, encircles, encapsulates, oris otherwise securely fastened around a coil spring 34 using a supportplate 35 an anchor nut 36, thus retaining the energy stored in thespring. In a preferred embodiment, the retaining band may be made out ofsteel. The inner bent-shaped end of the spring 38 is designed to besecurely and slideably received within a vertical slot 42 in shaft 40 tofacilitate the transfer of the spring's stored energy to rotate theshaft 40 in a clock-wise or counter clock-wise direction around theY-Axis, depending on the rotational direction of the spring's outputforce.

As further illustrated by FIG. 2, FIG. 4A, and FIG. 4B, the springhousing 20 may be a substantially u-shaped housing having a circularside wall 22, an end wall 24 at one end of the side wall 22, wherein theother or opposite end of the side wall 22 may be open to receive thepower spring assembly 30. One embodiment of the present invention mayinclude a flange 26, that may circumscribe the lower, open end, of theside wall 22, and gasket 23 which may be interposed betweencorresponding surfaces of the spring cover plate 50 and the outer end ofside wall 22. A central opening 29 may be provided in the end wall 24which may house a bearing 64 to receive the lower end of the shaft 44 ina slip-fit manner. In the preferred embodiment, an O-ring 66 may bereceived within an O-ring receptive groove of the central opening 29 forproviding an air- or fluid-tight fit between the one end of shaft 40 andthe spring housing 20.

As illustrated in FIG. 2A, FIG. 2B, FIG. 4A, and FIG. 4B, the shaft 40may be slideably received in the inner part of the spring 34 wherein theinner end of the spring 38 may be received within a vertical slot 42 ofshaft 40 thereby attaching or securing, though releasably, the powerspring assembly 30 and the shaft 40. The power spring assembly 30 andthe shaft 40 attached or secured thereto are in turn disposed withinspring housing 20, with the spring 34 received on the inside surface ofthe end wall 24 and the lower end of the shaft 44 received in end wall'scentral opening 29. In the preferred embodiment, the lower end of theshaft 44 may be slip-fittedly received in a bearing 64 housed in the endwall's central opening 29. The anchor nut 36 may be slideably receivedwithin a vertical slot 21 in the spring housing circular side wall 22and may be accessed through the side wall opening 25. A bolt 62 isprojected through the side wall opening 25 and mated with the anchor nut36 on the retaining band 32 securing together the spring housing 20 andthe power spring assembly 30. The assembly depicted in FIGS. 4A and 4B,illustrating the shaft 40, releasably secured to the power springassembly 30 which is in turn secured to the spring housing 20 by a bolt62 is herein referred to as the spring housing assembly.

A spring cover-plate 50 may define the removable top portion of thespring-return operator 10. A central opening 52 may be provided in thecover-plate 50 to receive the upper end of the shaft 46. The preferredembodiment may also include an O-ring 58 which may be received within anO-ring receptive groove in the lower end of the cover-plate 50 forproviding an air- or fluid-tight fit between the spring housing 20 andthe cover-plate 50, and the spring-return operator 10 in general. Theopenings 54 in the cover-plate may be used to secure or fasten the coverplate with a power actuator using bolts 80, thus securing and engagingthe spring-return operator 10, with a power actuator, such as apneumatic vane actuator 12 as shown in FIG. 1B. The spring housingassembly of FIG. 4 may be securely fastened, by means of bolts 60, whichproject through openings in the peripheral flange 27 and the openings inthe lower end of the cover plate 56, and may be mated or otherwisesecured with nuts 68.

As illustrated in FIG. 5 a retainer device 80 may be slideably mated,fitted, or coupled with the bottom side of the shaft 44 and securelyscrewed or fastened to the spring housing 20 using bolts 82 that may betied into the threaded openings 28 of the spring housing's end wall 24.With the retainer device fitted or mated with the bottom side of theshaft 44 and thus the shaft itself 40, and secured to the springhousing, the shaft 40, and thus the spring 34 to which it is secured,may be locked in place within the spring housing 20, allowing for thesafe unfastening and removal or separation of the spring housingassembly from the cover-plate 50 by loosening and removing the nuts 68and bolts 60, and thus disengaging the spring housing assembly from thepower actuator 12.

The ability to lock the spring using the retainer device allows for thesafe and in-the-field manual winding and unwinding of the spring-returnpower operator 10. To illustrate the unwinding of the spring, withrespect to the assembly depicted in FIGS. 1A and 1B as an example, thespring-return operator 10 is illustrated as coupled with a pneumaticvane actuator 12 and a valving member 14, and to unwind the spring 34,the shaft 40 is rotated in a counter-clockwise output direction aroundthe Y-Axis for the spring-return 10 and the depicted vane actuator 12.Once the spring is unwound, the coupled or engaged vane actuator 12 andspring-return operator 10 may be unfastened and removed or separatedfrom the valving member 14 by undoing or removing whatever means wasused to secure and engage the spring-return operator to the plug shaft15 of the valving member 14. Removing the air pressure applied to theair port opening of vane actuator 19 allows the spring-return operatorto rotate shaft and the vane of the vane actuator 12 counter-clockwiseas far as allowed by the stop bolt 18, thus partially or fully unwindingthe spring 34. As illustrated in FIG. 5 and explained above, the springretainer device may be used to lock the shaft 40, and thus the spring34, in place. With the spring locked, nuts 68 bolts 60 may be removed,and the spring housing assembly removed, separated or disengaged fromthe cover-plate 50 and the vane actuator 12. With the housing assemblyremoved, separated or disengaged, air pressure through the vane actuatorair port opening 19 may be used to fully rotate the vane of the vaneactuator in the clockwise direction, and thus away from the opening 19and the stop bolt 18. The housing assembly may then be reengaged withthe vane actuator 12 and securely fastened to the cover-plate usingbolts 60 and nuts 68 thereby reengaging the spring-return actuator 10and the vane actuator 12. Air pressure may thereafter be applied throughthe air port opening 19 until the spring and the actuator torques are inbalance. With the spring and the actuator torques in balance, the springretainer bolts 82 may be removed and the spring retainer device 80removed, separated, or disengaged from the shaft 40. The air pressureapplied through the air port opening 19 may then be removed therebyallowing the spring 34 to rotate the shaft 40 and thus the vane of thevane actuator in the counter-clockwise direction as far as allowed bythe stop bolt 18. The aforementioned steps may be repeated to releasethe entire tension of the spring 40. The foregoing description is onlyan example of releasing the spring tension utilizing a pneumatic vaneactuator and as such, the embodiments of the present invention mayutilize other actuators or devices in releasing the spring tension.

Once the spring's tension is released as described above, the retainingband 32 provides for the safe removal of the spring assembly from theshaft 40 and spring housing 20 once the bolt 62 is removed from theanchor nut 36. As such, the direction of the spring output rotation maybe reversed by simply rotating the spring 34 180 degrees along theX-Axis. Therefore, the retaining band enables the user to reverse theoutput direction of the spring-return actuator 10 in the field.

As illustrated in FIGS. 6A-6F, the multi-slot shaft 40 of the preferredembodiment enables the user to adjust the spring preload to accommodatedifferent air supply pressures to the spring-return operator 10. FIG. 6Aillustrates the bent-shaped end part of the spring 38 secured to slot 1which represents the assembly at 0% reduction in spring preload. Thebolt 62 may be removed and the spring 34, retained in the retaining band32, may be slideably removed, separated, or disengaged from the shaft40. The shaft 40 may then be rotated such to allow the bent-shaped endpart of the spring 38 be slideably secured to slot 2 as illustrated inFIG. 6B. As also illustrated in FIG. 6B, slot 2 correspond to a 18degree clockwise reorientation of the shaft, as illustrated by theorientation of the square cavity 98 within the shaft, used forillustration purposes only. This adjustment allows for a 4% reduction inspring preload. As further illustrated in FIGS. 6C-6E, securing thebent-shaped end part of the spring 38 to slots 3, 4, or 5 of the shaft40 results in a 8%, 12%, or 16% reduction in the spring preload,respectively.

Once the direction of the spring is reversed, or the spring is securedto the appropriate slot on the shaft corresponding to a desirable springpreload, the spring made be wound using a similar methodology. Toillustrate the winding of the spring, again take the assembly depictedin FIG. 1 as an example, wherein the spring-return operator is coupledwith a pneumatic vane actuator 12 and a valving member 14, and similarlyassume a counter-clockwise output direction around the Y-Axis for thespring-return 10 and the vane actuator 12. With the vane actuator 12rotated fully counter-clockwise, couple or engage the spring-returnoperator 10 with the vane actuator 12. Air pressure through the vaneactuator air port opposite to the air port opening 19 may now be appliedto fully rotate the vane of the vane actuator in the clockwisedirection, and thus away from the opening 19 and the stop bolt 18. Asillustrated in FIG. 5 and explained above, the spring retainer devicemay be used to lock the shaft 40, and thus the spring 34, in place. Withthe spring locked, nuts 68 bolts 60 may be removed, and the springhousing assembly removed, separated or disengaged from the cover-plate50 and the vane actuator 12. With the housing assembly removed,separated or disengaged, air pressure through the vane actuator air portopposite to the air port opening 19 may be applied to fully rotate thevane of the vane actuator in the counter-clockwise direction, andtowards the air port opening 19 and the stop bolt 18. The housingassembly may then be reengaged with the vane actuator 12 and securelyfastened to the cover-plate using bolts 60 and nuts 68 therebyreengaging the spring-return operator 10 and the vane actuator 12. Airpressure may thereafter be applied through the air port opposite to theair port opening 19 until the spring and the actuator torques are inbalance. With the spring and the actuator torques in balance, the springretainer bolts 82 may be removed and the spring retainer device 80removed, separated, or disengaged from the shaft 40. Air pressurethrough the air port opening 19 may then be applied to move the vaneactually fully clockwise thereby winding the spring 34. Theaforementioned steps may be repeated to wind the spring 40 to adesirable level. In a preferred embodiment, the spring may be wounduntil the air pressure to balance the spring and the actuator is halfthe supplied air pressure (80 psi upper supply pressure limit).

The foregoing disclosure and description of various embodiments of theinvention are illustrative and explanatory thereof, and various changesin the details of the illustrated spring-return actuator and the methodof using the same may be made without departing from the scope of theinvention. For example, a pneumatic vane actuator is not required towind or unwind the spring 34 of the spring return operator 10. Asillustrated in FIG. 7, a device 90 designed specifically for measuringand adjusting spring tension may be utilized wherein the operator 10 maybe secured to the device 90 using an adapter 92 and an actuator 94 maybe used to insert or release tension on the spring of the operator 10 asmeasured by a torque measuring load cell 96.

We claim:
 1. A rotary spring-return operator comprising: a housinghaving a housing aperture; a cover plate having a cover plate aperture;a shaft having an upper end section, a lower end section, and a middlesection, wherein the middle section is multi-slotted and has a widerdiameter than the upper end section and the lower end section, andwherein the lower end section is capable of extending through thehousing aperture and the upper end section is capable of extendingthrough the cover plate aperture; a spring capable of being engaged tosaid shaft and capable of being received within the interior of saidhousing; and a retaining band adjacent the spring.
 2. The rotaryspring-return actuator of claim 1, wherein the retaining band is madeout of steel.
 3. The rotary spring-return operator of claim 1, whereinthe retaining band is secured to the housing.
 4. The rotaryspring-return operator of claim 1, wherein the rotary spring-returnoperator is engaged with a pneumatic vane actuator and wherein upon lossof air from the pneumatic vane actuator, the shaft is rotatable to adefined position as the spring is unwound.
 5. The rotary spring-returnoperator of claim 1, wherein the multi-slot shaft is slideably receivedwithin the interior part of the spring.
 6. The rotary spring-returnoperator of claim 1, further comprising a retainer device disposed onthe shaft and secured to the housing such that the shaft is locked inplace with the housing.
 7. A rotary spring-return actuator comprising: ahousing having a housing aperture; a cover plate having a cover plateaperture; a multi-slot shaft capable of extending through the housingaperture and the cover plate aperture; a bearing disposed in a centralopening in the housing, wherein the shaft can be slip-fittingly receivedin the bearing; and a spring capable of being engaged to said shaft andcapable of being received within the interior of said housing, whereinthe spring is rotatable to a defined position and securable to a slot inthe multi-slot shaft to adjust the preload on the spring-returnactuator.
 8. The rotary spring-return operator of claim 7, furthercomprising a retaining band adjacent to the spring.
 9. The rotaryspring-return actuator of claim 7, wherein the retaining band is madeout of steel.
 10. The rotary spring-return operator of claim 7, whereinthe retaining band is secured to the housing.
 11. The actuator of claim7, further comprising an o-ring disposed between the bearing and thecentral opening of the housing.
 12. A rotary spring-return operatorwhich comprises: a housing having a housing aperture; a cover platehaving a cover plate aperture; a shaft having an upper end section, alower end section, and a middle section, wherein the middle section ismulti-slotted and has a wider diameter than the upper end section andthe lower end section, and wherein the lower end section is capable ofextending through the housing aperture and the upper end section iscapable of extending through the cover plate aperture; a spring capableof being engaged to said shaft and capable of being received within theinterior of said housing; and a retaining band adjacent the spring. 13.The rotary spring-return actuator of claim 12, wherein the retainingband is made out of steel.
 14. The rotary spring-return operator ofclaim 12, wherein the retaining band is secured to the housing.
 15. Therotary spring-return actuator of claim 12, wherein the rotaryspring-return operator is engaged with a pneumatic vane actuator andused as a fail-safe device.
 16. A retaining band disposed in a rotaryspring-return operator, the rotary spring-return operator comprising ahousing with a slot formed therein, a shaft rotatably journaled withinthe housing, and a spring interposed between and secured relative tosaid shaft and the housing, wherein the retaining band has an anchordisposed thereon to secure the retaining band to the spring, the anchorbeing slidingly receivable within the slot, and wherein the retainingband encapsulates the spring and secures the spring to the housing. 17.The retaining band of claim 16, wherein the retaining band is made ofsteel.
 18. The retaining band of claim 16, wherein the anchor comprisesan anchor nut and a bolt mateable therewith.
 19. A multi-slot shaftdisposed in a rotary spring-return operator, the rotary spring-returnoperator comprising a housing that rotatably receives the multi-slotshaft, a spring interposed between and secured relative to themulti-slot shaft and the housing, wherein the multi-slot shaft isrotatable to a defined position and the spring is securable to a slot inthe multi-slot shaft to adjust the preload on the spring-returnoperator, and a bearing disposed in a central opening in the housing,wherein the shaft may be slip-fittingly received in the bearing.
 20. Theshaft of claim 19, further comprising an o-ring disposed between thebearing and the central opening of the housing.